Technological Field
The present invention relates to a fixing belt, a fixing device, and an image forming apparatus.
Description of the Related Art
A fixing device used in an image forming apparatus such as a copying machine or a laser beam printer generally brings a heated fixing belt into contact with a recording medium carrying an unfixed toner image so that the toner image is fixed onto the recording medium. In the fixing device, for example, one of two or more rollers supporting an endless fixing belt is a heating roller heating the fixing belt. Since the thermal capacity of the fixing belt is relatively small, the fixing device has an excellent fixing property and has an advantage in, for example, high-speed image formation.
As the fixing belt, there is known an endless fixing belt which includes a base layer made of polyimide and containing filler and other layers such as a heat-resistant elastic layer or releasing layer formed thereon, wherein a tensile elastic modulus is 5000 N/mm2 or more (for example, see JP 2001-215821 A). Since the fixing belt has high dispersibility of the filler in the base layer, the fixing belt is excellent in surface smoothness and thickness uniformity and is also excellent in mechanical strength and durability. Accordingly, even when the elastic layer or the releasing layer is further laminated thereon, it is possible to transport a recording medium for a long period of time while realizing a good fixing property.
Meanwhile, there is a demand for high-speed image formation in the above-described image forming apparatus. In the high-speed image formation, the fixing operation needs to be performed at a high speed. In general, the toner image is fixed by heating and pressing the toner image at a fixing nip portion. In the fast fixing, not only high-speed fixing but also an excellent separation property between the fixing belt and the recording medium on which the toner image is fixed is required. In order to satisfactorily separate the recording medium at the time of fixing, a releasing layer having excellent releasability is disposed on the surface layer of the fixing belt to solve a problem caused by the material of the fixing belt. However, this solution is not sufficient for the high-speed image formation in some cases.